A conventional joint elbow is usually molded in one piece. In the wiring operation, the friction drag of pulling a cable or wire through a plurality of joint elbows may increase whenever more joint elbows are added. The users often smear some grease on the outer coat of the cable or wire in order to decrease the friction drag of pulling the cable or wire. The contact of the grease with the outer coat of the cable or wire may cause the outer coat of the cable or wire to become fragile and easily break over an extended period of time. Moreover, the friction between the cable or wire and the joint elbows may damage the outer coat of the cable or wire and also reduce the durability of the cable or wire.
An improved joint elbow has at least one roller which is mounted on the inner wall of the improved joint elbow. However, in the wiring operation, a user has to bend a predetermined portion of a cable or wire in advance before he threads the cable or wire through the improved joint elbow. When a plurality of joint elbows are used in the wiring operation, the user has to bend the cable or wire several times before he can thread the cable or wire through all the joint elbows. The difficulty of bending and threading the cable or wire will increase whenever more joint elbows are added.